Project Summary/Abstract Barriers to understanding and intervening to ensure all children?s socioemotional adaptation to kindergarten entry include failure to acknowledge parents? adjustment to this milestone and a lack of consideration of biologically-based individual differences that determine the influence of the early environmental on outcomes. Although it has been acknowledged that parent-child interactions are dynamic and transactional, few empirical studies have assessed a transactional model of both children?s and mothers? adjustment to kindergarten. Further, models that acknowledge biological reactivity as moderators of the relation between environmental influence and adjustment outcomes have begun to emerge for children, but few studies examine parental outcomes, and virtually none examine both parent and child outcomes in the same study. This project will contribute to the scientific knowledge base of bidirectional parent-child influences, socioemotional adjustment to kindergarten, and biological susceptibility to the environment. A longitudinal, multimethod design will be used to test three specific aims. These aims will be examined in light of other well-established predictors of children?s kindergarten adjustment (academic readiness, effortful control, possible language and developmental delay, and environmental variables) and mothers? general adjustment (interpersonal support, sociodemographic information). Aim 1 is to test whether children?s biological reactivity moderates the extent to which maternal overcontrol predicts children?s adjustment difficulties. In previous phases of our broader longitudinal study, mothers were assessed observationally at two time points for overcontrolling parenting behavior. Children?s adjustment difficulties will be reported by parents and teachers. Children?s cortisol reactivity and autonomic reactivity were assessed previously, and a major contribution of the planned work is the assessment of children?s neural reactivity and regulation. Children will undergo EEG collection as part of the current project. Aim 2 is to test whether maternal biological reactivity moderates the extent to which children?s inhibited temperament predicts mothers? difficulties in adjusting to children?s entry into kindergarten. Multiple waves of temperament assessment, and maternal biological reactivity (cortisol, autonomic measures, EEG) are available from the parent grant. Assessing maternal adjustment difficulties will be a major contribution of new data collection. Finally, Aim 3 is to test a transactional model of parent-child adjustment. Incorporating significant interactions from the first two aims, we will test the simultaneous influences between children and mothers while controlling for intra-individual stability. Understanding transactional influences and how they are informed by individual differences in biological susceptibility to environmental influences will point towards innovative preventive interventions to help all children and their families successfully navigate kindergarten entry, aligning with the National Institute of Child Health and Human Development?s mission to ensure that all children reach their fullest potential.